Polyureas made from aminocrotonates

ABSTRACT

A compound having the formula below, where R is —H or —CH 2 —CH 3 ; n, x, y, and z are nonnegative integers; R 2  is an aliphatic group or oxyaliphatic group; and R 3  is an aliphatic group.

This application is a divisional application of allowed U.S. patentapplication Ser. No. 14/264,459, filed on Apr. 2, 2014, which is acontinuation-in-part application of U.S. Pat. No. 8,710,170, filed onMay 13, 2009 and issued on Apr. 29, 2014, which claims the benefit ofU.S. Provisional Application No. 61/053,226, filed on May 15, 2008. Theprovisional application and all other publications and patent documentsreferred to throughout this nonprovisional application are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure is generally related to polyureas.

DESCRIPTION OF RELATED ART

Polyurea coatings are based on the reaction of diamines and/orpolyamines with isocyanate hardeners. They may be characterized by fastcuring (e.g. seconds), a high elongation, a low tensile strength, andpoor adhesion to blasted steel. Due to their composition and low glasstransition temperature, they are also very permeable for watermolecules. Polyureas with such properties may be unfit for marine use.

Poly-urea coatings are commonly used as truck bed liners, secondarycontainment coatings and by the military as blast mitigation coatings.Polyureas are also widely used in fast curing injection molding systems.The general structure of polyureas is shown below for a diamine havingthe formula NH₂—R¹—NH₂ and an isocyanate having the formula OCN—X—NCO.

The polyamines used may in general be polyoxypropylene amines(Jeffamines), mixed with aromatic diamines. The isocyanate hardeners maybe polymeric aromatic isocyanates with a very low vapor pressure. Thevery high reactivity of amines with isocyanates constitutes a limitationfor this technology. For marine coatings applications, reducing thisreactivity may be desirable.

Aspartics have been used as reagents for isocyanates (U.S. Pat. Nos.5,126,170 and 5,236,741). Aspartic resins are the reaction products ofaliphatic diamines with diethylmaleate via the Michael AdditionReaction. The idea behind the aspartics is to reduce the reactivity ofthe secondary NH by steric hindrance by the bulky aspartic moiety. Theuse of cycloaliphatic diamines with methyl groups in the alpha positionresults in further reduction of the NH reactivity. Aspartics contain thestructure shown below.

Existing commercially available aspartic resins do have interestingcuring characteristics but they are too high in viscosity to allow forsolvent free coatings in general. Aspartic resins may not be suitablefor under water use in combination with cathodic protection systems.

Other well-known modifications of amines are ketimines and aldimines,which are the reaction products of primary amines with ketones oraldehydes. Their general structures are shown below.

Ketimines and aldimines can react with isocyanates in several ways.Ketimines and aldimines may react with moisture from the atmospheresplitting off the ketone or aldehyde. The generated free amine will thenreact with the isocyanate group (US Patent Application Publication No.2007/0060733). Although of interest this approach may not lead tosolvent free coatings. Ketimines or aldimines may also be used asreactive diluents in polyurethanes, aspartics, and polyureas.

BRIEF SUMMARY

Disclosed herein is a compound having the formula below. R is —H or—CH₂—CH₃. The values n, x, y, and z are nonnegative integers. R² is analiphatic group or oxyaliphatic group and R³ is an aliphatic group.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth in order to provide athorough understanding of the present disclosure. However, it will beapparent to one skilled in the art that the present subject matter maybe practiced in other embodiments that depart from these specificdetails. In other instances, detailed descriptions of well-known methodsand devices are omitted so as to not obscure the present disclosure withunnecessary detail.

Disclosed herein is a modification of polyamines which may change theproperties of the polyureas made therefrom. Aliphatic polyamines such asJeffamines are chemically modified into secondary amines with animproved gel time and different mechanical properties for the curedproducts. Without limiting the claims to any particular theory orreaction mechanism, it is believed that electron withdrawing groups maybe used to reduce the basicity of the NH groups to achieve the same orsimilar NH reactivity as with aspartics without relying on sterichindrance. The reaction product of a enamine, enaminone, or crotonatewith an isocyanate is an enurea.

Polyamines including aliphatic polyamines (which may include ethergroups) can be reacted with one or more beta ketoesters likeethylacetoacetate or diketones like acetylacetone. These compounds maybe made according to methods known in the art for making ketimines. Bothethylacetoacetate and acetylacetone are industrially available at lowcost. They may react spontaneously with Jeffamines or other polyaminesat ambient temperature. Water separates out and further drying can bedone by either azeotropic distillation or the use of molecular sieves inthe final formulation. The general reaction is shown below, followed bythe products made from ethylacetoacetate and acetylacetone. Othersuitable reactants include, but are not limited to, methylacetoacetateand t-butylacetoacetate.

These compounds may be in equilibrium with the tautomer enamineβ-aminocrotonate or β-aminoenone forms as shown below.

The R² and R³ groups from at least one side of the R¹ may also be joinedby a covalent bond to form a cyclic structure bonded to the amine. Forexample, the use of 1,3-cyclohexane-dione produces the aminoenone shownbelow.

Any polyamine or multiple polyamines capable of forming ketimines may beused, including but not limited to, primary polyamines, m-xylylenediamine, diethylene triamine, (2-aminoethoxy)-2-aminoethane,2-(2-aminoethoxy)ethanol, 1,5-diamino-2-methylpentane,N-methyl-1,3-aminopropane, NH₂—(CH(CH₃)—CH₂—O)_(x)—CH₂—CH(CH₃)—NH₂,NH₂—(CH(CH₃)—CH₂—O)_(x)—(CH₂—CH₂—O)_(y)—(CH(CH₃)—CH₂—O)_(z)—CH₂—CH(CH₃)—NH₂,NH₂—(CH₂)_(x)—O—CH₂—CH₂—O—(CH₂)_(x)—NH₂, orNH₂—(CH(CH₃)—CH₂—O)_(x)—CH₂—CR[(CH₂)_(n)—(O—CH₂—CH(CH₃))_(y)—NH₂]—CH₂—(O—CH₂—CH(CH₃))_(z)—NH₂.In these formulas n, x, y, and z are nonnegative numbers, including butnot limited to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and higher values, andmay represent average values of a mixture of such compounds. Thecompounds containing ethoxy groups are commercially available asJEFFAMINES®, including the D series, ED series, EDR series, and Tseries. The polyamine need contain at least two reactive amines, thoughsome amines may possibly remain unreacted in the polymer. If there arethree or more amine groups, it is not necessary that all the amines bereactive to form ketimines, such as secondary or tertiary amines. Ifthere are only two reactive amines in the compound (bi functional), thanthe polyisocyanate may have at least three isocyanate groups (at leasttrifunctional). If the amine has at least three reactive amines, than adiisocyanate may be used. It should be noted that both reactants mayalso be trifunctional or more.

The electron withdrawing effect across the double bond and subsequentreduction in NH reactivity may be more efficient than in the case of theaspartics. The general reaction with a polyisocyanate is shown below forthe case of a diamine and a diisocyanate. The R¹ group may containadditional reactive amines, including —NH—CR³═CH—CO—R², and/or the R⁴group may contain additional isocyanate group to form a crosslinkedpolymer. Since combinations of multiple reactants may be used, the Rgroups may be different in different repeat units of the polymer.

Any reactive isocyanate may be used optionally subject to thefunctionality requirement described above, including but not limited to,diphenylmethane-containing polyisocyanate, toluene diisocyanate,diphenyl methane diisocyanate, hexamethylene diisocyanate dimers andtrimers, 4,4′-dicyclohexylmethane-diisocyanate, isophorone diisocyanate,tetramethylxylene diisocyanate, hexamethylene diisocyanate,cycloaliphatic polyisocyanates, aliphatic polyisocyanates, adduct oftoluene diisocyanate and glycerin, biuret of toluene diisocyanate, andbiuret of hexamethylene diisocyanate. More than one isocyanate may beused in a polymer. At least 50 mol % of the polyisocyanate moleculesreacting with the polyamine are aromatic polyisocyanates having at leastone aromatic group. The aromatic group may have double bonds conjugatedwith the isocyanate groups. Any purely aliphatic polyisocyanates wouldbe less than 50, 20, 10, 5, or 1 mol % of the polyisocyanates, oraliphatic polyisocyanates may be completely absent.

Any method of combining the isocyanate with the above compounds may beused to form the polymer. One suitable method of combining is to applyto a surface an amine composition comprising the above compounds and anisocyanate composition comprising the polyisocyanate, such that amixture of the amine composition and the isocyanate composition isformed during the application. For example, the application may be byspraying the compositions onto the surface and allowing the mixture tocure to a polyurea coating. Additional coating methods and formulationcomponents are disclosed in US Patent Application Publication Nos.2007/0060733 and 2007/0261602.

The reactants may have relatively low viscosities, and be liquid at roomtemperature. Thus the reaction may be performed in the substantialabsence of solvent or in a lack of solvent. When no solvent is used, novolatile compounds are released during the reaction. There may be lessthan 5 or 1 wt % of any solvents or liquids other than the tworeactants. The reaction may be performed at room temperature or atambient temperature without external or active heating.

The reaction products of these crotonates and amino-enones may showimproved mechanical properties, beyond what can be achieved withaspartics and/or polyureas. Some characteristic properties of the curedproducts may include:

-   -   VOC and HAPS: zero    -   Viscosity of base resin: 1,000 cps Brookfield    -   Equivalent NH weight: 240-300    -   Tensile strength: 7,000 -10,000 psi    -   Elongation at break for clear films: 10-20%    -   Glass transition: 90-125° C.    -   Tack free time at 20° C.: 10 minutes    -   Good mechanical properties: 12 h    -   Full cure: 3 to 5 days    -   Over coating interval: 3 to 5 days    -   Direct adhesion to blasted steel: excellent    -   Raw material cost for base resin: US$ 2/lbs

The resin system may be formulated into coatings with a 1 to 1 or 2 to 1ratio. The coatings have zero VOC or HAPS and may be dry to touch in tenminutes. Good mechanical properties may be obtained overnight and fullcure after 3 to 5 days. The fully cured material or coating may be freeof any solvents or liquids. New upcoming International MaritimeOrganization (IMO) rules may result in a serious loss of productivity inthe ship building industry. The new polyurea may offer increasedproductivity due to the curing rate and the possibility of single coat“multi pass” application, combined with a suitable over coating window.

As water scavengers, molecular sieves, p-toluene sulfonyl isocyanate,vinyl silanes or other silanes or any other way of drying the resins andpigments may be used as is normally done in the polyurethane industry.

The modified polyamines are also candidates for improved compositematerials and injection molding materials. By varying the backbone ofthe diamines and polyamines it is possible to freeze in the curingreaction at ambient temperature in order to make prepregs. The prepregscan then be fully formed and heat cured at a later stage. Glasstransition temperatures of up to 125° C. with a curing time of 10minutes at 90° C. have been obtained.

The following examples are given to illustrate specific applications.These specific examples are not intended to limit the scope of thedisclosure in this application. All reactions are carried out in a threenecked flask, equipped with a mechanical stirrer or magnetic stirringbar.

EXAMPLE 1

Crotonate of MXDA—To the reactor were added 5 moles of m-xylylenediamine (680 grams) and 10 moles of ethyl acetoacetate. The reaction wasslightly exothermic. The reactor was equipped with a distillation headand the mixture was slowly heated to remove the reaction water. Theremoval of the reaction water can be done either at ambient pressure orunder reduced pressure or by means of an azeotropic distillation usinghexane, cyclohexane, toluene, xylene, or other. At ambient pressure thereaction was virtually complete when all the reaction water is removed(180 grams) at about 145° C.

It is possible to make use of a combination of a reduced pressure,ambient pressure, and/or an azeotropic distillation process. Residualwater content can be as low as 5 ppm. In order to push the reaction tocompletion it may be advantageous to use a slight excess of one of theingredients, such as the ethyl acetoacetate. The reaction between theamine and ethyl acetoacetate is spontaneous and does not require the useof any catalyst. The obtained bifunctional amino crotonate can be curedadvantageously with aromatic polyfunctional isocyanates.

EXAMPLE 2

Crotonate of Jeffamine D230—850 grams of Jeffamine D230 (7.39 molarequivalent weight) and 960 grams of ethyl acetoacetate were reacted asin Example 1. The resulting NH equivalent weight was 227.

EXAMPLE 3

Crotonate of Jeffamine T403—521 grams of Jeffamine T403 (3.21 molarequivalent weight) were reacted with 423 grams of ethyl acetoacetate asin Example 1. The resulting NH equivalent weight of the polymer was 274.

EXAMPLE 4

Enaminone of Jeffamine T403—1001 grams of Jeffamine T403 (6.18 molarequivalent weight) were reacted with 803 grams of ethyl acetyl acetoneas in Example 1. A small excess of 20 grams of ethyl acetoacetate wasadded. The resulting NH equivalent weight was 244.

EXAMPLE 5

Crotonate of diethylene triamine—160 grams of diethylene triamine (DTA)(1.55 molar equivalent) was reacted with 403 grams of ethyl acetoacetateas in Example 1. The resulting product was rather dark in color butcured well with aromatic isocyanates. The resulting crotonate NHequivalent weight was 164. Note that the product still has the NH aminefunctionality in the middle.

EXAMPLE 6

Enaminone of glycol amine—420 grams of glycolamine (4 moles) werereacted with 4 moles of acetyl acetone as in Example 1. The reaction wasexothermic and cooling was required. The resulting product had a NHequivalent weight of 187.

EXAMPLE 7

Crotonate of Dytek A (methyl diamino pentane)—2 moles of Dytek A werereacted with 4 moles of ethyl acetoacetate as in Example 1. Theresulting product had an NH equivalent weight of 129.

EXAMPLE 8

Crotonate of N-methyl-1,3-propane diamine—2 moles ofN-methyl-1,3-propane diamine were reacted with 2 moles of ethylacetoacetate as in Example 1. The resulting crotonate NH functionalitywas 200. Note that the product still had the NH-CH3 functionality at theother end.

EXAMPLE 9

Crotonate of Jeffamine XTJ566—950 grams of XTJ566 (6.5 equivalentweight) were reacted with 851 grams of ethyl acetoacetate as inExample 1. A small excess of ethyl acetoacetate (50 grams) was added tofacilitate the completion of the reaction. The resulting NHfunctionality of the resin obtained was 257.

EXAMPLE 10

Crotonate of Jeffamine EDR176—750 grams of EDR176 (8.5 equivalentweight) were reacted with 1108 grams of ethyl acetoacetate as inExample 1. The resulting product had an NH equivalent weight of 200.

EXAMPLE 11

Enaminone of Jeffamine T403—1100 grams of Jeffamine T403 (6.79equivalent weight) were reacted with 680 grams of ethyl acetone as inExample 1. The reaction water was removed azeotropically withcyclohexane and followed with a vacuum distillation the resultingproduct was light in color and had an enaminone NH functionality of 244.The residual moisture content of the resin was lower than 10 ppm.

EXAMPLE 12

Enaminone of Jeffamine D230—1000 grams of Jeffamine D230 (8.69equivalent weight) were reacted with 869 grams of acetyl acetone as inExample 1. The resulting product had an enaminone equivalent weight of197.

EXAMPLE 13

Solvent free fast curing polycrotonate—2000 grams of T403 crotonateresin (equivalent weight of 274) were mixed in a cowless mixer with 1000grams of TiO₂ pigment, 600 grams of Talcum filler, 35 grams of Byk 163wetting agent, and 15 grams of coroc flow additive. As a waterscavenger, 100 grams of molecular sieves were added.

The resulting paint can be cured with aromatic isocyanates like MondurCD, MRS4, MRS light (all Bayer) and Rubinate M and or suprasec 9584 fromHuntsman Chemicals. This example can be performed with any of themonomers and isocyanates disclosed herein. The amounts of the materialsmay be varied.

Obviously, many modifications and variations are possible in light ofthe above teachings. It is therefore to be understood that the claimedsubject matter may be practiced otherwise than as specificallydescribed. Any reference to claim elements in the singular, e.g., usingthe articles “a,” “an,” “the,” or “said” is not construed as limitingthe element to the singular.

What is claimed is:
 1. A compound having the formula:

wherein R is —H or —CH₂—CH₃; wherein n is a nonnegative integer; whereinx, y, and z are positive integers; wherein R² is an aliphatic group oroxyaliphatic group; and wherein R³ is an aliphatic group.